Generally there is a need for devices to accurately position a probe onto an animal for infusing drugs or hormones into different ventricles, for removing fluids from ventricles to study the changes in hormones due to such removal, for probing the thalamus and hypothalamus by the use of electrical probes to stimulate parts of the brain, to record electrical brain activity, and for implanting crystalline steroids or peptide hormones into the brain by use of a probe through cannula.
Various types of devices have been devised for doing one or more of the above mentioned functions, such as U.S. Pat. Nos. 3,542,030 to Hoffman et al and 3,817,249 to Nicholson. In the Hoffman et al device, the animal must be restrained while the device is in use. This can be difficult to do and also causes the animal to be excited, which may affect the function of the brain that the scientist wishes to study. Furthermore, it may be necessary to drug the animal in order to use the device which also can affect the function of the brain to be studied.
In the Nicholson device, a removable grid plate is implanted in an animal's skull for positioning electrodes in an animal's brain. While this device is functional for positioning electrodes, there is a need for a head mounted stereotaxic apparatus which is more versatile and which does not have the disadvantages of the prior art referred to above.